1. Field of the Invention
The present invention relates to transmission/reception of channel state information (CSI) in a multi-carrier wireless communication system, and more particularly to a design and implementation of a CSI feedback channel in a multi-carrier wireless communication system.
2. Description of the Related Art
With the development of cellular type wireless mobile telecommunication systems in the U.S. toward the end of the 1970's, voice communication service is provided to users through an advanced mobile phone service (AMPS) system, which is a 1st generation (1G) analog type mobile communication system. A 2nd generation (2G) mobile communication system called a “Code Division Multiple Access (CDMA) system” followed in the—1990's to provide users with voice and low-speed data services.
An IMT-2000 (International Mobile Telecommunication-2000), which is a 3rd generation (3G) mobile communication system, has been researched at the end of the 1990's to provide improved wireless multimedia services, international roaming, and high-speed data services. Recently, IMT-2000 services have been partially provided to users to transmit high-speed data and accommodate the increase of data in modern mobile communication systems. To do so, the 3G mobile communication system uses a packet service communication system. Packet service communication systems can transmit burst packet data to a plurality of mobile stations, so it is adaptable for transmitting mass-storage data.
In short, the packet service communication system has been developed to provide high-speed packet services. For instance, a high-speed downlink packet access (HSDPA) scheme suggested by the 3GPP (3rd Generation Partnership Project), which is a consortium for providing standards for 3rd generation asynchronous mobile communication systems, adopts an adaptive modulation and coding (AMC) scheme, a hybrid automatic retransmission request (HARQ) scheme, and a fast cell select (FCS) scheme to support high-speed packet data transmission.
Hereinafter, the AMC scheme will be described as an example of high-speed packet service schemes.
The AMC scheme is a data transmission scheme capable of improving cell efficiency by selecting the channel modulation scheme and the coding scheme according to the channel status between a base station and a mobile station. According to the AMC scheme, a plurality of modulation schemes are incorporated with a plurality of coding schemes to perform modulation and coding for channel signals. Generally, a set of the modulation scheme and the coding scheme is called a “Modulation and Coding Scheme (MCS)”, and a level (1 to N) of the MCS can be determined according to the number of MCSs. That is, according to the AMC scheme, the level of the MCS is adaptively determined depending on the channel status between the mobile station and the base station, thereby improving a system efficiency of the base station. In addition, the AMC scheme, HARQ scheme, and FCS scheme can be used not only for the HSDPA scheme, but also for various high-speed data transmission schemes.
The 3G mobile communication system has evolved into a 4th generation (4G) mobile communication system. The 4G mobile communication system is being standardized to provide an effective combination of a wired communication network and a wireless communication network and total services in addition to the wireless communication services provided by conventional communication systems. Thus, it is necessary to develop a technique capable of transmitting as much mass-storage data as a wired communication network through a wireless communication network.
To this end, an OFDM (Orthogonal Frequency Division Multiplexing) scheme has been actively studied to transmit high-speed data through wired/wireless channels in the 4G mobile communication systems. According to the OFDM scheme, a multi-carrier is used to transmit data. The OFDM scheme is a kind of an MCM (Multi Carrier Modulation) scheme, in which serial symbol arrays are converted into parallel symbol arrays, which are modulated into a plurality of sub-carriers, that is, a plurality of sub-carrier channels which are orthogonal to each other.
The basic idea of the above-mentioned communication systems is to effectively and reliably transmit data through a channel. A next-generation multimedia mobile communication system, requires a high-speed communication scheme capable of processing and transmitting various data types, such as images and wireless data, while simultaneously providing a basic voice service, so it is necessary to improve the efficiency of mobile communication systems by applying a proper coding technique.
However, this is extremely difficult as wireless communication systems are prone to errors from various factors, such as multipath interference, shadowing, wave attenuation, noise, interference, and fading, thereby causing information loss. Such an information loss may distort a transmission signal, causing performance degradation of the mobile communication system. Various studies and research have been conducted to reduce information loss and improve reliability of mobile communication systems by applying various techniques to the system according to the status of its channels.